Characteristics of Hip Dysplasia in Adults With Cerebral Palsy

BACKGROUND: With increased life expectancy, cerebral palsy (CP) is no longer solely a pediatric condition. Among adults with CP, orthopaedic conditions and associated pain represent the most prevalent challenges. Hip dysplasia is one of the most common conditions affecting adults with CP; however, the research remains limited, and clear follow-up guidelines are currently lacking. This study aimed to investigate the prevalence and severity of hip dysplasia in adults with CP and identify related factors. Our goal is to create a foundation for developing follow-up methods and clinical screening for specific groups of adults with CP at risk for worsening hip dysplasia. METHODS: This retrospective study examined hip radiographs of 331 adults with CP (aged 18 y or older) from (removed for blinding) between 2011 and 2021. Migration percentage (MP) and Melbourne Cerebral Palsy Hip Classification System (MCHCS) were used to assess hip displacement. Patient factors, including age, sex, Gross Motor Function Classification System (GMFCS) level, pain condition and treatment, and spasticity management were analyzed. Linear regression models examined associations between patient factors and MP, while ordered logistic regression assessed relationships between GMFCS and MCHCS. RESULTS: The mean MP across all participants was 23.2% (SD: 15.3), with 24.5% showing hip subluxation (MP>30%). GMFCS level was strongly associated with hip displacement, with GMFCS IV and V showing significantly higher MP values (Parameter Estimate=16.29 and PE=14.20, respectively; both P<0.01). Among GMFCS I/II, MP increased with age (PE=0.10, P=0.046), while no significant age associations were found in other GMFCS groups. MCHCS was also associated with GMFCS level, especially GMFCS IV and V (both P <0.0001). Notably, 21.6% of GMFCS I/II subjects were MCHCS 4 or higher. CONCLUSIONS: Hip dysplasia remains prevalent in adults with CP, with GMFCS level being the strongest predictor of displacement severity. Those with GMFCS I/II may experience progressive displacement with aging, while severe displacement in higher GMFCS levels may develop earlier. These findings emphasize the potential importance of understanding the natural history of the hip in CP into adulthood for all GMFCS levels. LEVEL OF EVIDENCE: Prognostic study level II-retrospective study.